Explanation

In CH₄ (methane), the carbon is sp³ hybridized.

It giving a tetrahedral geometry with bond angles of 109.5°.

Explanation

Phenol is weakly acidic and dissolves in aqueous NaOH to form sodium phenoxide → giving a clear, colorless homogeneous solution.

It does not dissolve completely in water or Na₂CO₃ because it is not acidic enough to react fully with weaker bases.

Explanation

Electrolysis of water requires an external supply of electrical energy to break bonds → endothermic.

Condensation and freezing release heat (exothermic processes).

Explanation

A catalyst is not consumed during a chemical reaction; it remains unchanged at the end.

It works by lowering activation energy and providing an alternate pathway for the reaction.

Explanation

Molecular crystals are held together by weak van der Waals forces or hydrogen bonds.

Examples include crystals of ice, iodine, naphthalene, etc.

Explanation

Elements in the same group have the same number of valence electrons, so their chemical properties remain similar.

However, their reactivity trends (increase or decrease) may vary down the group, but overall chemical nature stays roughly the same.

Explanation

 Henry Cavendish discovered the composition of water, establishing the basis for its chemical equation H2O

 This discovery was made through experiments conducted in 1781, with the results published in 1784. 

Explanation

By definition, 1 mole of any element contains Avogadro’s number (6.022 × 10²³) of atoms.

So, 1 mole of a metal has the same number of atoms as 1 mole of hydrogen atoms.

Explanation

Step 1: Identify the process
The equation is:

$$\text{<b><font color="\#0000ff">Na</font></b>}<b><font\; color="\#0000ff">(</font></b>\mathrm{<b><font\; color="\#0000ff">g</font></b>}<b><font\; color="\#0000ff">)</font></b><b><font\; color="\#0000ff">\to </font></b>{\text{<b><font color="\#0000ff">Na</font></b>}}^{<b><font\; color="\#0000ff">+</font></b>}<b><font\; color="\#0000ff">(</font></b>\mathrm{<b><font\; color="\#0000ff">g</font></b>}<b><font\; color="\#0000ff">)</font></b><b><font\; color="\#0000ff">+</font></b>{\mathrm{<b><font\; color="\#0000ff">e</font></b>}}^{<b><font\; color="\#0000ff">-</font></b>}$$

This is the ionization of gaseous sodium atoms.

Step 2: Enthalpy change definition
The enthalpy change for removing 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous positive ions is the first ionization enthalpy (or energy).

Explanation

Bleaching powder (Ca(OCl)Cl) releases chlorine, which is a strong oxidizing substance.

This property makes it useful for bleaching and disinfection.